Rhodium(III)‐catalyzed chelation‐assisted highly regio‐ and stereoselective direct olefination of imidazoles with olefins has been developed. A broad range of C2‐substituted N‐(2‐pyrimidyl)imidazoles underwent smooth C5‐olefination with both activated and unactivated olefins to furnish the corresponding products in good to excellent yields with high tolerance of functional groups on both coupling partners in the presence of a cationic rhodium(III) catalyst. The combination of a catalytic amount of Cu(OAc)₂ (copper(II) acetate) and O₂ (oxygen) serves as the terminal oxidant. This protocol strongly relies on the use of 2‐substituted imidazoles as the substrates, and the presence of readily installable and removable pyrimidyl directing group was found to be critical for catalysis. Mechanistic studies suggest the involvement of a five‐membered rhodacycle as the key intermediate in the catalytic cycle. The method can also be extended to the coupling reaction of benzimidazoles with olefins.

中文翻译：

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铑（III）催化的咪唑选择性直接烯烃化

已经开发了铑（III）催化的螯合辅助的咪唑与烯烃的高度区域和立体选择性直接烯烃化反应。广泛的C2取代的N-（2-嘧啶基）咪唑在活化和未活化的烯烃下均进行了平滑的C5烯烃化反应，从而以较高的收率提供了相应的产品，并且在存在偶合剂的情况下，两个偶合伙伴对官能团的耐受性都很高阳离子铑（III）催化剂。催化量的Cu（OAc）₂（醋酸铜（II））和O _2的组合（氧气）作为末端氧化剂。该方案强烈依赖于使用2-取代的咪唑作为底物，并且发现易于安装和移动的嘧啶导向基团的存在对催化至关重要。机理研究表明，五元罗丹环是催化循环的关键中间体。该方法还可以扩展到苯并咪唑与烯烃的偶联反应。